A major objective sought in the proposed research is to elucidate the molecular mechanisms underlying the actions of neurotransmitters, with emphasis on norepinephrine and acetylcholine, on the turnover of the individual lipid phosphate and their physiological significance in the iris muscle. It is well established that the metabolism of phosphatidic acid (PA), phosphatidylinositol (PI) and, from our recent work, triphosphoinositide (TPI) is associated with the effects of neurotransmitters on nerve and muscle. The initial effect of these neurotransmitters appears to be on the breakdown, rather than biosynthesis. This we have demonstrated in vitro in the past year. To extend these findings, we propose to carry out the experiments on muscle which was prelabelled with P32 and/or (H3) myo inositol in vivo. To throw more light on the physiological significance of the phospholipid effect, our recent finding on the effect of superior cervical ganglionectomy and electrical stimulation on the turnover of PA, PI and TPI of the iris will be extended.